Desalting crude oil



Patented May 28,' 1946' I DESALTING emma on.

Application rely i4, i945, serial No. 605,061

11 Claims.

This invention relates to improvements in the removal of inorganic salts and/or water from crude oils, particularly crude petroleum oils. Inorganic salts in the form of chlorides of sodium, magnesium and/or calcium are frequently associated with crude petroleum oils, usually in the form of a salt brine emulsiied with oil, or in the form of crystalline salts, usually surrounded by an oil lm. The removal of salt from such crude oils by the usual methods presents dimcult problems. For example, when contacting the saltcontaining crude oil with water, the oil film upon the salt particles prevents the water from coming in contact withthe salt crystal and as a consequence, methods employing the washing of crude oil with water are not eiective. Even the addition of a demulsifying agent to the water frequently has relatively small effect. The present aqueous phases to separate.

invention provides a method for reducing the water and salt content of crude oil to a relatively low ngure.

The removal of salt from crude oils prior to any distillation process, such as a cracking process, is desirable since the presence of these salts, particularly when the concentration thereof exceeds about pounds of salt per 1000 barrels oi' oil gives rise to considerable dimculties. They form deposits upon the heating surfaces and in the tubes of the heating equipment, such es stills, heat exchangers, and the like, reducing the elciency thereof; such deposits plug lines and give rise to serious corrosion problems.

It is an object of the invention to provide an improved method of removing water and salt from crude oils. Another object of the invention is to provide a method oi removing water and inorganic salts, such as chlorides of sodium, magnesium and/or calcium from crude petroleum oils. Still another object of the invention is to provide a method of obtaining crude petroleum oils of relatively low water and salt-content from crude petroleum oils containing relatively large amounts of water and inorganic salts, while' combining this process with extraction of the oil with anhydrous HF in a later stage.

In accordance with the present invention,

vwater and/or salt-containing crude petroleum' oils, particularly such oils having more than about 20 Vpounds of salt per 1000 barrels of oil.-

are eflectively-desalted and substantially freed ot water by treating thesame with hydrogen nuoride and water azeotropic or constant boiling lmixture, although aqueous hydrogen uoride used. The presence of large `amounts of inorganic chlorides, such as sodium, calcium and magnesium chlorides in crude oils is highly undesirable since as hereinbefore stated, the presence of such salts inoils 'subjected to various distillation and/or heating processes undergo hydrolysis which produces hydrochloric acid. Dry hydrochloric acid itself does little damage, but when dissolved in Water it becomes very corrosive. Raw petroleum crude oil as obtained from the oil Well contains relatively large amounts of water, usually emulsied with the oil. Usually the bulk of the water in crude oil is separated therefrom by placing the oil and water mixture in a settling tank and. permitting 'the oil and Other well-known means are often employed. The treatment of water and salt-containing crude oils with an azeotropic mixture of hydrogen fluoride and water provides a unique method of simultaneously freeing the crude oil of its majorl proportion of water and inorganic salts and in many cases results in a crude oil substantially free oi'water and' inorganic salts. Hydrogen fiuoride forms an azeotrope with water which contains about 36% by weight of hydrogen fluoride and boilsat about 248 F. at atmospheric pressure. This azeotrope or constant boiling mixture, is capable of taking up additional water, which property makes it particularly well-suited for the herein-described purpose. The treatment of salt-containing crude oil with the hydrogen iluoride converts the metal chlorides, yparticularly the alkali metal and the alkaline-earth metal chlorides to the water insoluble fiuorides. These inorganic tluorides being less readily hydrolyzed than are the chlorides do not form corrosive products; furthermore, any oi the remaining inorganic salts settle out more readily due to the emulsion. destabilizing effect of the hydrogen uorlde azeotrope treatment.

Azeotropic aqueous hydrouoric acid is in? fluoride being extremely hygroscopic absorbs water in the course of processing. These Water solutions of hydroiluoric acid must generally be removed from the hydrogen iluor'ide to preserve its activity for the process in question. Removal of this' water is mostconveniently eil'ected by simple distillation to produce the constant boiling water-'HF' mixture as a residue. The hydrogen uorlde water mixture vresulting from the `suited for this process.

dehydration and desalting of crude oil treatment with a hydrogen fluoride water azeotrope can be distilled to give a side cut having substantially the composition of the hydrogen fluoride water azeotrope which can then be recycled for further use in dehydrating and desalting crude oil. The process of the present invention can be carried out in one or more stages, concurrently cfr countercurrently. Conventional equipment for example, empty or packed towers or mixing equipment, can be used.

Suitable operating temperatures fall Within the range of from about F. to about 200 F. and preferably within .the range of about 60 F. to about 100 F., temperatures of about 65 F. to about '75 F. having been found particularly well Depending upon the reaction temperatures and the concentration of hydrogen fluoride employed, pressures of from about atmospheric pressure to about 150 pounds per square inch can be used in the lcontacting step with contact time varying from about 1 minute to about 120 minutes or more. The amount of hydrogen fluoride employed in the reactor should be sufiicient to maintain an aqueous hydrogen fluoride mixture having a concentration of from about 15% to about 50%. preferably about 36% hydrogen fluoride.

Briefly, the present invention comprises contacting crude oil containing water and inorganic chlorides with a hydrogen fluoride-water mixture containing from about 15% to about 50% hydrogen fluoride, and preferably a constant boiling mixture thereof, separating as a raffinate a crude y oil substantially free of water and inorganic salts, which is ready for further processing, and an extract phase comprising aqueous hydrogen fluoride containing dissolved therein inorganic fluorides,

out the invention, the description serving to exemplify the same. A crude oil containing water, inorganic chlorides and other' undesirablesalts, for example, 100 to 200 lbs. per 1000 barrels is introduced via line I0 into the bottom portion of a contactor II containing a body of aqueous hy- I I comprising aqueous hydrogen fluoride containing inorganic fluorides is Withdrawn from contactor I I via line I1 and introduced into a stripper I8 provided with heating means I 9 in the bottom portion thereof and cooling or dephlegmating means 20 in the 'upper portion thereof. A bottom temperature of about'250 F.`to 300 F. is maintained in the botvtom of stripper I8 while a temperature of from about 50 F. to about 100 F. is maintained in the top portion of the stripper I8 by means of the dephlegmating coils 20. 4An aqueous hydrogen fluoride side stream is Withdrawn from the stripper I8 via line 2I and introduced into side stripper or reboiler 22 provided with heating coils 23 for maintaining a temperature of about 248 F. for withdrawing a constant boiling hydrogen fluoride-water stream via line 24, which if desired can be recycled to the contactor I3 via line I6. The overhead from stripper 22 is returned to the stripper I8- via line 25. 'Water and/or aqueous hydrogen chloride is taken off from the top of the stripper I8 through a line 26, while inorganic fluorides are Withdrawn from the bottom of stripper I8 through aline 21.

The treated crude oil from the contactor I3 substantially free of inorganic salts and water, is Withdrawn from the contactor I3 vla line 28 and introduced into asettler 29 to facilitate the separation of any aqueous hydrogen fluoride which may be carried over with the treated crude oil. Any aqueous hydrogen fluoride separating in the settler 29 1s withdrawn therefrom and returned to the contactor I3 vla line 30. Hydrogen chloride, formed in the conversion of the inorganic chlorides to the fluorides, is vented from the system through line 3|. By eliminating the hydrogen chloride from the system at this point and from the stripper I8 and the contactors, as hereinbefore described, hydrochloric acid corrosion difficulties in subsequent equipment are substantially eliminated.

The treated crude oil from the settler 29 may be subjected to any desired subsequent treatment. As an example of such subsequent treatment, the crude oil, substantially freed of inorganic salts and water may be subjected to extraction with anhydrous hydrogen fluoride, and the extract therefrom heated to obtain a hydrogen fluoridedrogen fluoride introduced thereinto through line I2 from a contactor I3 by means of a Dump I4. After passing through the aqueous hydrogen fluoride in the contactor II the crude oil is passed via line I5 to the bottom portion of contactor I3 containing a body of hydrogen fluoride-Water azeotrope introduced vla line I3 from a source hereinafter described.l Contactors II and I3 are maintained at a temperature of from about 32 F. to about 100 F., preferably from about '10 F. to about 80 F. by suitable means (not shown) and under a pressure sufficient to maintain the reactants in the liquid phase. Under these conditions, the inorganic chlorides are converted tol the corresponding fluorides with formation of hydrogen chloride. 'I'he latter may be removed from the system through vents II-a and/or I3a. While I have shown a two-stage contacting step for Water azeotrope which may be recycled to the crude on desaiting stage. Thus the desalted and dehydrated crude oll from, the settler 2,9 can be withdrawn therefrom through line 32 and introduced into contactor 33, wherein it is countercurrently contacted with anhydrous hydrogenl fluoride introduced into the upper portion from and line 36. Anhydrous hydrogen fluoride makeup, if necessary, can be introduced into the system via line 36a. The contactor 33 can be malntalned at a temperature of from about 0 F. to about 150 F. and preferably from aboutI 70 F. to

about F. by means of coils 33a and under a pressure sufficient to maintain the products in the liquid phase. A raiilnate is withdrawn from the top of contactor 33 through a line 31 and introduced into a settler 38 wherein any hydrogen fluoride extract, which may have been carried over with the raffinate is permitted to settle out and returned tothe contactor 33 via line 39. The ralnate from the settler 38 can then be introaaodeea I Y overhead from the stripper l via line td and condenser 155 and introduced into a receiver fit, provided with a vent d1. If desired, the hydrogen fluoride and light hydrocarbons in the receiver 68 may be recycled to the contacter 33 via pump d8 and line 49.

The extract from the contactor 33 lcomprising aqueous hydrogen fluoride and sludge-like material can be withdrawn from the contactor 33 via line G and introduced into stripper 5i pro- -vided with heating coils 52 in the bottom portion thereof and dephlegmating coils E3 in the upper portion thereof. A bottom temperature of about 250 F. to about 300 F. is suitably maintained in the stripper 5i while a top temperature of about 100 F. to about 125 F. is maintained in the upper portion thereof. Anhydrous hydrogen iluoride is taken overhead from the stripper 5i via line 5d and condenser 55 and passed into the .hydrogen fluoride receiverl. The extract, freed of hydrogen iiuoride, can be withdrawn from the bottom of the stripper 5i via line 5t.

Water accidentally entering contactor 33 nds its way to stripper 5i. To remove it, a side cut of hydrogen fluoride from the stripper 5i is withdrawn through a line 51 and introduced into a. side stripper 53 provided with a heating coil 59 to maintainA a temperature somewhat below 248 F. therein. vazeotrope is Withdrawn from the bottom of side stripper 58 via line t0 and, if desired, recycled to the crude oil pretreating stage via line it. Hydrogen fluoride from the side stripper 5B passes oi overhead via line 6i and is returned to the stripper 5 l I Hydrogen iiuoride-water azeotrope from other sources can be introduced into the system via line e2 and excess HF-HzO can be withdrawn at this point.

Although I have exemplied my invention by reference tothe removal of water and salts from crude petroleum oil, the invention is applicable to the removal of salts from reduced crude petroleum oils. While I have illustrated and described a method of carrying outmy invention, other variations and modifications can be made therein Without departing from the spirit of the invention or the scope of the appended claims.

l. The method oi removing water and inorganic salts from crude oil containing the same comprising contacting said crude oil with a hydsogen fluoride-water mixture containing not more than 56% IIR-separating an oil phase comprising crude petroleum oil substantially free of water and inorganic salts, and an aqueousphase A hydrogen uoride-Water a crude petroleum oil containing the same, comprising contacting said crude oil with a hydrogen iiuoride-water mixture in an amount and for a time sumcient to convert said chlorides to fluorides with the formation of hydrogen chloride, separating an oiiI phase comprising substantially crude petroleum o il substantially free of water and inorganic salts, and an aqueous phase, comprising hydrogen iiuoride, water and inorganic fluorides, and removing said hydrogen chloride from the system.

4. The method of removing water and inorganic salts comprising inorganic chlorides from a crude petroleum oil containing the same, comprising contacting saidl crude oil with a hydrogen fluoride-Water mixture in suiicient quantities and under conditions to convert said chlorides to luorides with the formation of hydrogen chloride, removing hydrogen chloride from the contacting zone, separating an oil phase comprising crude petroleum oil substantially free of water' and inorganic salts and an aqueous phase comprising hydrogen uoride, water and inorganic iiuorides.

5. The 'method of removing water and inox' ganic salts from crude petroleum oil as described in claim 4 in which the inorganic chlorides are selected from the group consisting of alkali metal chlorides and alkaline earth chlorides.

6. The method of removing Water and in organic salts comprising inorganic chlorides from crude petroleum oil comprising contacting said crude oil with a hydrogen iiuoride-water mixture quantities and under conditions to convert said chlorides to uorides withv the formation of hydrogen chloride, separating an oil phase, comprising said crude oil substantially free of inorganic salts, and an extract phase comprising aqueous hydrogen iiuoride and inorganic iiuorides, removing hydrogen chloride from the contacting zone, separating the .oil phase from the extract phase, separating a hydrogen iiuoride water azeotrope mixture from said extract, and recycling said hydrogen fluoride Water azeotrope mixture to saidcontact zone.

7. The method of removing water and inorganic salts comprising inorganic chlorides from a crude petroleum oil containing the same comprising contacting said crude oil in a contacting zone with a hydrogen fluoride-water azeotrope mixture insufficient quantities and under conditions to convert said chlorides to fiuorides, with comprising hydrogen fluoride. water and inorgroup consisting of alkali metal chlorides and alkaline earthA chlorides.

3. 'Ihe method of removing water and inorganic salts'comprising inorganic chlorides from the formation of hydrogen chloride, and to form a diphasic .separation of a ramnate phase comprising said crude oil substantially free of water and inorganic salts and an extract phase comprising aqueous hydrogen fluoride and inorganic iiuoride's, removing hydrogen chloride from the system, separating said ramnate from said extract, contacting said raffinate with Aliquid anhydrous hydrogen fluoride in suicient quantities to form a diphasic separation of a second ramnate phase. and a second extract phase comprising tract, and recycling said hydrogen fluoride-vvater azeotrope mixtures to said'ilrst crudev oil contacting zone.

8. The method of removing water and inorganic salts from a crude petroleum oil as described in claim 7 in which the inorganic chlorides are selected from the group consisting of alkali metal chlorides and alkaline earth chlorides.

9. The method of desaltingva crude petroleum oil containing inorganic chlorides comprising contacting said crude oil with a hydrogen-fluoridewater azeotrope mixture in an amount and for a time suflicient to convert said fluorides to chlorides with the formation of hydrogen chloride, and removing said hydrogen chloride.`

10. The method of desalting the crude petroleum oil as described in claim 9 in which the inorganic chlorides are selected from the group consisting of alkali metal chlorides and alkaline earth chlorides.

11. The method of rening crude petroleum containing undesirable salts and water wl:y .ch comprises extracting said salts and Water from said oil by contacting with aqueous hydrofluoric acid of not more than 50% concentration, treating the resulting extracted oil with substantially anhydrous HF to dissolve aromatic constituents therefrom and produce an aromatic extract and a refined oil, recovering anhydrous HF from said oil and said aromatic extract and recycling it to said treating operation, and recovering a constant boiling HF-water azeotropic mixture from said aromatic extract for recycle to said rst extraction step.

' VANDERVEER VOORHEES. 

